Fair Value of Financial Instruments - Derivative Fair Value Measurements, Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2022	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Total derivative assets valued with prices provided by models and other valuation techniques (as a percent)	6.00%
Total derivative liabilities valued with prices provided by models and other valuation techniques (as a percent)	2.00%
Change in credit reserve	$ 5	$ 11

This element represents the portion of total fair value of all derivative assets, which are valued using various valuation techniques including internal models based on a fundamental analysis of the market and extrapolation of observable market data with similar characteristics.

No definition available.

Name:	nrg_DerivativeAssetFairValueDeterminedUsingValuationTechniquesPercentage
Namespace Prefix:	nrg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant